Absorbents and process for producing the same, absorbable constructs and absorbable articles

ABSTRACT

Absorbents comprising an water-absorbable resin and water-insoluble nonporous spherical monoparticles having an average diameter of 1 to 50 nm; a process for producing these absorbent by mixing the spherical monoparticles, which have been solubilized in water, with dry powdery particles of the water-absorbable resin; absorbable constructs composed of the above absorbent with a matrix wherein the amount of the absorbent ranges from 30 to 95% by weight based on the absorbable construct; and absorbable articles provided with the absorbable construct, a liquid-permeable sheet and an air-permeable back sheet. These absorbents, absorbable constructs and absorbable articles are excellent in the diffusion/absorption speed and absorption amount of a liquid within the resin even in case of absorbing a liquid containing water-insoluble or hardly water-soluble matters such as menstrual blood or feces.

TECHNICAL FIELD

The present invention relates to absorbents and a process for producingthe same, absorbable constructs and absorbable articles. Morespecifically, the present invention relates to absorbents and a processfor producing the same, absorbable constructs and absorbable articles,all of which have an excellent diffusion/absorption speed and anabsorption amount of the liquid absorbed within an absorbable resin evenin case the liquid to be absorbed contains water-insoluble or hardlywater-soluble matters such as menstrual blood or feces.

BACKGROUND ART

Up to now, various methods have been proposed for improving theabsorption speed of water-absorbable resins which are used as absorbentsfor a paper diaper and the like, some of them as described below arebased on a concept of increasing the area contacting with a liquid to beabsorbed by broadening the surface area of the water-absorbable resins.

-   a. A method of rendering a water-absorbable resin porous by adding a    low-boiling point volatile solvent to a polymerization solution to    be used in the manufacturing process of the water-absorbable resin,    and vaporizing the volatile solvent with polymerization heat    (Japanese Patent Application Laid-Open No.S59-18712 (1984));-   b. A method of forming a foam type resin by blending a carboxyl    group-containing water-absorbable resin and glycidyl    group-containing polyolefin resin with a crosslinking agent and    pyrolytic foaming agent, and then foaming the mixture with heat    (Japanese Patent Application Laid-Open No.S63-251437 (1988));-   c. A method for obtaining a porous water-absorbable resin by    dispersing a foaming agent consisting of an azo compound containing    an amino group into an aqueous solution containing an unsaturated    monomer and crosslinking agent, and by conducting polymerization    (Domestic Re-publication of PCT Publication No. WO96/17884);-   d. A method of granulating fine particles using water, a hot-melt    resin binder and the like;-   e. A method of coating the surface of a water-absorbable resin in a    composition with porous inorganic particles so that the weight ratio    of the resin to the inorganic particles falls within a range of    10/90 to 90/10, wherein the composition consists of a mixture of    particles of the water-absorbable resin and the inorganic particles    (Japanese Patent Application Laid-Open No.H8-10616 (1996)).

However, these methods were not sufficient in terms of performance and aproduction process.

Further, it has recently been suggested to improve the absorption speedby a method in which the surface area of a water-absorbable resin isincreased by least 10% by building a micro-filler into thewater-absorbable resin (International Publication No. WO99/03577).

In said method, the improvement of the absorption speed is recognizedfor a liquid to be absorbed containing water-insoluble or hardlywater-soluble matters such as menstrual blood or feces, however, thefurther improvement of the absorption speed and absorption amount of theliquid is desired because of the increased demand from the market.

The inventors have intensively studied considering the above-mentionedproblems, and as a result, have reached to the present invention with afinding that the diffusion/absorption speed and absorption amount of aliquid to be absorbed are improved by using a water-absorbable resinobtained by polymerization in the presence of a complex compound (d) ofa metal element (d1) and a ligand (d2) in which the ligand is an anionor a neutral molecule, in combination with a water-insoluble nonporousspherical monoparticle having a specific average particle diameter.

The present invention is directed to provide absorbents having anexcellent diffusion/absorption speed and absorption amount of a liquidto be absorbed inside the absorbable resin, and to provide a process forproducing the same, wherein the liquid to be absorbed containswater-insoluble or hardly water-soluble matters such as menstrual bloodor feces. Further, the another purpose of the present invention is toprovide absorbable constructs and absorbable articles showing anexcellent absorption performance when the absorbents of the presentinvention are applied to sanitary goods such as a sanitary napkin.

SUMMARY OF THE INVENTION

Namely, the present invention is the invention described in (I) through(IV) below.

(I) Absorbents (C) comprising a water-absorbable resin (A) andwater-insoluble nonporous spherical monoparticle (B) having an averageparticle diameter of 1 to 50 nm, and said (A) is a water-absorbableresin obtained by polymerization in the presence of a complex compound(d) of a metal element (d1) and a ligand (d2) in which the ligand is ananion or a neutral molecule.

(II) A process for producing absorbents (C) by mixing said (B) inwater-solublizing state with the dry powdery particle of said (A).

(III) Absorbable constructs (F) composed of a matrix of said absorbents(C) and a fibrous material (E), wherein the amount of said absorbents(C) is 30 to 95% by weight based on said absorbable constructs (F).

(IV) Absorbable articles (G) provided with said absorbable constructs(F), a liquid-permeable sheet and an air-permeable back sheet.

DETAILED DISCLOSURE OF THE INVENTION

(Absorbents and a Process for Producing the Same)

As the water-absorbable resins (A) mentioned herein, for example,crosslinked starch-acrylic acid salt copolymers, saponifiedstarch-acrylonitrile copolymers, crosslinked polyacrylic acid salts,self-crosslinked polyacrylic acid salts, saponified crosslinked(meth)acrylic ester-vinyl acetate copolymers, crosslinkedisobutylene/maleic anhydride copolymers, crosslinked polysulfonic acidsalts, crosslinked polyacrylic acid salt/polysulfonic acid saltcopolymers, crosslinked polyacrylic acid/polyacrylamide copolymers,crosslinked polyacrylamide and hydrolysis products thereof, crosslinkedpolyvinylpyrrolidone, crosslinked derivatives of cellulose and the likeare can be mentioned.

Among these, preferable water-absorbable resin is a resin which canabsorb and hold a large quantity of liquid by ion osmotic pressure andhas a polymerizable monomer containing a carboxylic acid salt and/or acarboxylic acid as a main constituent, which monomer gives less leakageof liquid even though a load or an external force is added, andcrosslinked starch-acrylic acid salt copolymers and crosslinkedpolyacrylic acid salts are further preferable.

The kind of the salt and its degree of neutralization are notparticularly limited when (A) is a resin in the form of a salt(neutralized salt). The kind of the salt is typically, for example, analkali metal salt, preferably a sodium or potassium salt and the degreeof neutralization for its acid group is typically 50 to 90 mol %,preferably 60 to 80 mol %. The timing of neutralization may be before orafter polymerization.

The water-absorbable resin (A) of the above-mentioned crosslinkedpolyacrylic acid salts is a water-absorbable resin obtained bypolymerizing a water-soluble monomer (a-1) and a first crosslinkingagent (a-2).

As the water-soluble monomer (a-1) used for producing (A), what can beexemplarily mentioned is a radically polymerizable water-soluble monomerhaving a carboxylic group, sulfonic acid group and phosphoric acidgroup, and a salt thereof.

As the radically polymerizable water-soluble monomer having a carboxylicgroup, what can be exemplarily mentioned is an unsaturated mono- orpolycarboxylic acid [(meth)acrylic acid (which means acrylic acid and/ormethacrylic acid. Hereinafter, the same description is used), crotonicacid, sorbic acid, maleic acid, itaconic acid, cinnamic acid], its saltor the like, or an anhydride thereof [maleic anhydride or the like],etc.

As the radically polymerizable water-soluble monomer having a sulfonicacid group, for example, what can be mentioned is a fatty acid or anaromatic vinyl sulfonic acid (vinyl sulfonic acid, allyl sulfonic acid,vinyltoluene sulfonic acid, styrene sulfonic acid and the like),sulfoalkyl (meth)acrylate [sulfoethyl (meth)acrylate, sulfopropyl(meth)acrylate or the like], (meth)acrylamido alkylsulfonic acid[2-acrylamido-2-methylpropanesulfonic acid or the like], or a saltthereof, etc.

As the radically polymerizable water-soluble monomer having a phosphoricacid group, for example, such as a (meth)acrylic acid hydroxyalkylphosphoric acid monoester, [2-hydroxyethyl(meth)acryloyl phosphate,phenyl-2-acryloyloxyethyl phosphate and the like] can be mentioned.

These may be used alone, or 2 or more of them may be used incombination. Among these, the preferable water-soluble monomer is aradically polymerizable water-soluble monomer having a carboxylic groupand the salt thereof, more preferably an unsaturated mono- orpolycarboxylic acid and the salt thereof, and particularly preferable is(meth)acrylic acid or a salt thereof.

As the crosslinking agent used for producing (A), there are a firstcrosslinking agent (a-2) used in combination at polymerization of theabove monomer, and a surface-crosslinking agent (a second crosslinkingagent; a-3) which crosslinks the surface of particle which is preparedas needed by dry-pulverizing after polymerization. As (a-2), forexample, what can be mentioned is a crosslinking agent having 2 or moreethylenically unsaturated groups, crosslinking agent having at least onefunctional group which can react with the functional group of themonomer and having at least one ethylenically unsaturated group,crosslinking agent having at least 2 or more functional groups which canreact with the functional group of the monomer, or the like.

-   (i) As the crosslinking agent having 2 or more ethylenically    unsaturated groups, such as N,N′-methylenebis(meth)acrylamide,    ethylene glycol di(meth)acrylate, polyethylene glycol    di(meth)acrylate, propylene glycol di(meth)acrylate, glycerin (di or    tri)acrylate, trimethylolpropane triacrylate, triallylamine,    triallylcyanurate, triallylisocyanurate, tetraallyloxyethane,    pentaerythritol triallyl ether can be mentioned.-   (ii) As the crosslinking agent having at least one functional group    which can react with the functional group (for example, a carboxyl    group) of the monomer and having at least one ethylenically    unsaturated group, a crosslinking agent having at least one    functional group which can react with a group such as a carboxylic    acid (salt), hydroxyl, amino group and at the same time having at    least one ethylenically unsaturated group, and so on can be    mentioned, and for example, an ethylenically unsaturated group    having an epoxy group such as glycidyl (meth)acrylate etc. and an    ethylenically unsaturated group having a hydroxy group such as    N-methylol(meth)acrylamide or hydroxyethyl (meth)acrylate, and the    like can be mentioned.-   (iii) The crosslinking agent having at least 2 or more functional    groups which can react with the functional group of the monomer is a    crosslinking agent having at least 2 or more functional groups which    can react with a group such as a carboxylic acid (salt), hydroxyl,    amino group, and as examples of such crosslinking agent, such as a    polyglycidyl ether compound having 2 to 10 epoxy groups in a    molecule [ethylene glycol diglycidyl ether, glycerin-1,3-diglycidyl    ether, glycerin triglycidyl ether, polyethylene glycol diglycidyl    ether (the polymerization degree of polyethylene glycol is 2 to    100), polyglycerol polyglycidyl ether (the polymerization degree of    polyglycerol is 2 to 100) and the like]; a polyol compound of from    divalent to 20-valent [glycerin, ethylene glycol, polyethylene    glycol (the polymerization degree is 2 to 100) and the like]; a    polyamine compound of from divalent to 20 valent [ethylenediamine,    diethylenetriamine and the like]; a polyamine-based resin having a    molecular weight of 200 to 500,000 (polyamide polyamine    epichlorohydrin resin, polyamine epichlorohydrin resin, and the    like), an alkylene carbonate [ethylene carbonate and the like], an    azilidine compound, a polyimine compound can be mentioned. These    crosslinking agents may be used alone, or 2 or more of them may be    used in combination.

The amount of the first crosslinking agent (a-2) used is preferably0.001 to 5.0% by mass based on the total mass of the monomer (a-1) andthe first crosslinking agent (a-2), more preferably 0.002 to 2.0% bymass, and the amount 0.003 to 1.6% by mass is particularly preferred.When the amount of (a-2) is 0.001% by mass or more, the abilities ofwater retention/blood retention/absorption become good, and when 5.0% bymass or less, the crosslinking is not too strong and also the abilitiesof water retention/blood retention/absorption do not decrease.

The production process of the water-absorbable resin (A) in the presentinvention may be process which has been conventionally known, such as asolution polymerization process using an initiator, emulsionpolymerization process, suspension polymerization process, reverse-phasesuspension polymerization process, thin film polymerization process,spray polymerization process can be mentioned. As a method forcontrolling polymerization, an adiabatic polymerization method,temperature-control polymerization method, isothermal polymerizationmethod and the like can be mentioned. When a suspension polymerizationprocess or reverse-phase suspension polymerization process is applied tothe production process, the polymerization is carried out in thepresence of a conventionally known dispersing agent, protective colloid,surfactant or a mixture of one or 2 or more of them if necessary.Further, in case of a reverse-phase suspension polymerization process,the polymerization is carried out using a conventionally known solventsuch as cyclohexane, n-hexane, n-heptane and xylene. The solutionpolymerization process employing a polymerization initiator ispreferable, and an aqueous solution polymerization process isparticularly preferred because it does not require an organic solventand the like, and thus it is advantageous from the viewpoint of theproduction cost.

As an initiator, a conventionally known initiator can be used withoutparticular limitation as long as the initiator is an azo type initiator,peroxide type initiator, redox type initiator or organic halogenatedcompound initiator. Specifically, those initiators described below canbe mentioned.

-   (i) As the azo type initiator, azobisisobutylonitrile,    azobiscyanovaleric acid and its salt, 2,2′-azobis(amidinopropane)    dihydrochloride, 2,2′-azobis(2-amidinopropane) hydrochloride,    2,2′-azobis[2-methyl-N-(2-hydroxyethyl)]propionamide and the like;-   (ii) as the peroxide type initiator, an inorganic peroxide [hydrogen    peroxide, ammonium persulfate, potassium persulfate, sodium    persulfate and the like], an organic peroxide [benzoyl peroxide,    di-t-butyl peroxide, cumene hydroperoxide, succinic acid peroxide,    di(2-ethoxyethyl)peroxydicarbonate and the like];-   (iii) as the redox type initiator, a combination of a reducing agent    such as a sulfite or bisulfite of an alkali metal, ammonium sulfite,    ammonium bisulfite, ferric chloride, ferric sulfate, ascorbic acid,    and with an oxidizing agent such as a persulfate of an alkali metal,    ammonium persulfate, hydrogen peroxide, organic peroxide can be    mentioned.-   (iv) The halogens of the organic halogenated compound initiators are    fluorine, chlorine, bromine and iodine.

Though there is no particular limitation for the organic halogenatedcompound, what is preferred from the viewpoint of the polymerizabilityis an organic halogenated compound having a halogen atom number of 1 to10 or more and having a carbon atom number of 1 to 15 or more, selectedfrom a group consisting of a halogenated alkyl, halogenated alkyl phenylketone, halogenated alkylcarboxylic acid and alkyl ester of halogenatedalkylcarboxylic acid. Tetrachloromethane, trichlorobromomethane,trichloroiodomethane, dichloromethyl phenyl ketone,1-bromo-1-methylethylcarboxylic acid and an alkyl ester of1-bromo-1-methylethylcarboxylic acid wherein the alkyl group has acarbon atom number of 1 to 8 (for example, methyl 1-bromo-1-methylethylcarboxylate, ethyl 1-bromo-1-methylethyl carboxylate, octyl1-bromo-1-methylethyl carboxylate, and lauryl 1-bromo-1-methylethylcarboxylate) are more preferred. Dichloromethyl phenyl ketone and analkyl ester of 1-bromo-1-methylethyl carboxylic acid in which the carbonnumber in the alkyl group is 1 to 8 are particularly preferred.

These initiators may be used alone, or 2 or more of them may be used incombination. The azo type initiator, the redox type initiator and acombination of both are preferable. The amount of the initiator used ispreferably 0.005 to 0.5% by mass based on the total mass of (a-1) and(a-2), more preferably 0.007 to 0.4% by mass and particularly preferably0.009 to 0.3% by mass.

Further, it is preferable to make said (A) have a high molecular weightin order to enhance the absorption performance of the water-absorbableresin (A) of the present invention, and for the above purpose said (A)can be obtained by any one of the methods of 1) through 3) describedbelow.

-   1) Polymerization is carried out under a condition in which the    concentration of the total amount of (a-1) and (a-2) in a    polymerization liquid is 20% by mass or less.-   2) Polymerizing 70% by mass or more of the polymerizable monomers    ((a-1) and (a-2)) in the polymerization liquid at a constant    polymerization temperature of 60° C. or less, wherein the controlled    range for the constant temperature is preferably ±5° C., and more    preferably ±2° C.-   3) Polymerization is carried out in the presence of a complex    compound (d) of a metal element (d1) and a ligand (d2), in which the    ligand is an anion or a neutral molecule.

As the water-absorbable resin (A) of the present invention, the oneobtained by 3) is particularly preferred.

The complex compound (d) is a complex compound of a metal element (d1)and a ligand (d2) of an anion or a neutral molecule, and has a structurein which (d1) is surrounded by the ligand (d2) of an anion or a neutralmolecule.

As for (d1), there is no particular limitation so far as it is a metalelement, and for example, the IA Group element metal (lithium, sodium,potassium, cesium and the like), IB Group element metal (copper, silver,gold and the like), IIA Group element metal (magnesium, calcium, bariumand the like), IIIA Group element metal (scandium, yttrium and thelike), IIIB Group element metal (aluminum, gallium, indium, thallium andthe like), IVA Group element metal (titanium, zirconium, hafnium and thelike), IVB Group element metal (tin, zinc and the like), VA Groupelement metal (vanadium, niobium, tantalum), VB Group element metal(antimony, bismuth and the like), VIA Group element metal (chromium,molybdenum, tungsten), VIB Group element metal (tellurium, polonium andthe like), VIIA Group element metal (manganese, technetium, rhenium),VIII Group element metal (iron, cobalt, nickel, ruthenium, rhodium,palladium, osmium, iridium, platinum), Lanthanoid Group element metal(lanthanum, cerium and the like), the Actinoid Group element metal(actinium, thorium and the like) and the like, all of which are theprincipal group element metals, can be mentioned. From the viewpoint ofthe polymerizability of a vinylic polymerizable monomer, the IB Group,IIIA Group, IVA Group, VA Group, VIA Group, VIIA Group, VIII Group andLanthanoid Group element metals are preferable, the IB Group, VIII Groupand Lanthanoid Group element metals are more preferable, and the IBGroup and VIII Group element metals of the 4^(th) to 6^(th) period areparticularly preferable. From the viewpoint of easy-to-handleworkability and so on, the VIII Group element metals of the 5^(th)period (ruthenium, rhodium, palladium) are most preferable.

Though said (d1) exists usually as a cation, it can be otherwise than acation, for example, it may be neutral as iron pentacarbonyl.

(d2) is not specifically limited so far as it is a ligand being an anionor neutral molecule, but for example, 1) the anion of an atom selectedfrom hydrogen and halogen, 2) a compound having one or two or more atomsselected from nitrogen, oxygen, phosphorous and sulfur, and 3) one ortwo or more compounds selected from conjugated system compounds.

Specifically, those described below can be mentioned.

-   1) The anion of an atom selected from hydrogen and halogen;    -   the anion of hydrogen, fluorine, chlorine, bromine and iodine;-   2) As the compound having one or two or more atoms selected from a    group consisting of nitrogen, oxygen, phosphorous and sulfur, those    described below can be mentioned. A compound having a molecular    weight of 1,000 or less is preferable (those having the possibility    that the kind of coordination is 2 or more were classified in either    group suspected to coordinate).-   (1) Tertiary phosphine compounds having 1 to 4 or more phosphorous    atoms and 3 to 42 or more carbon atoms;

trimethylphosphine, triethylphosphine, diethylphenylphosphine,triphenylphosphine (hereinafter, referred to as PPh₃),ortho-phenylenebis(diphenylphosphine),ortho-phenylenebis(dimethylphosphine),ortho-phenylenebis(diethylphosphine),ortho-phenylenebis(ethylphenylphosphine),1,2-bis(diphenylphosphino)ethane, 1,2-bis(dimethylphosphino)ethane(hereinafter, referred to as dppe), 1,2-bis(diethylphosphino)ethane,1,2-bis(ethylphenylphosphino)ethane, 1,2-bis(diphenylphosphino)methane(hereinafter, referred to as dppm), 1,2-bis(dimethylphosphino)methane,1,2-bis(diethylphosphino)methane, 1,2-bis(ethylphenylphosphino)methane,tris(diphenylphosphinoethyl)phosphine,tris(diethylphosphinoethyl)phosphine,tris(dimethylphosphinoethyl)phosphine,tris(ethylphenylphosphinoethyl)phosphine, and the like;

-   (2) Ammonia or amines having 1 to 4 or more nitrogen atoms and 0 to    44 or more carbon atoms;-   (2-1) the number of nitrogen atom is 1; pyridine (hereinafter,    described as py), diethylamine, salicylamine, aminoethaneselenole,    2-hydroxy-6-methylpyridine, 2-(diethylamino)ethanol,    bis(2-aminoethyl)amide, ethanolamine, 2-aminoethanol, β-alanine,    2-hydroxy-6-methylpyridine, 3-salicylideneamino-1-propanol,    2-pyrrolidone, 8-quinolinol, salicylaldimine, α-picoline and the    like;-   (2-2) the number of nitrogen atom is 2; ethylenediamine    (hereinafter, referred to as en), propylenediamine,    trimethylenediamine, 1,2-cyclohexanediamine,    N,N-diethylethylenediamine, N,N-dimethylethylenediamine,    salicylideneethylenediamine, N-ethylsalicylaldiamine,    bis(benzoylacetone)ethylenediamine, 1,2-diamino-1,1′-dimethylethane,    2,2′-bipyridine (hereinafter, referred to as bpy),    2,2′-bipyridin-3-ine, 2,2′-bipyridine-N,N′dioxide, dicyandiamidine,    (aminoiminomethyl)urea, [(2-aminoethyl)amino]-1-propanol,    2-[(3-aminopropyl)amino]ethanol,    N-2[2(diethylamino)ethyl]-3-amino-1-propanol,    tris[2-(methylamino)ethyl]amine, imidazole,    N,N′-disalicylidenetrimethylenediamine,    4,6,6-trimethyl-3,7-diazanona-3-en-1,9-diol,    N,N,N′,N′-tetramethylethylenediamine, 1,8-naphtylidine, and the    like;-   (2-3) the number of nitrogen atom is 3 or more; diethylenetriamine,    triethylenetetramine, tetraethylpentamine,    N,N′-bis(2-aminobenzylidene)ethylenediamine,    tris[2-(methylamino)ethyl]amineaminopyridine,    1,3-bis[bis(2-pyridylethyl)aminomethyl]benzene,    4-dimethylamino-2,3-dimethyl-1-phenyl-5-pyrazolane, biguanide,    imidodicarbonimidediamide, biuret, carbamoylguanidine,    phthalocyanine, N,N,N′,N′-tetrakis(2-aminoethyl)ethylenediamine,    1,2,3-triaminopropane, tris(2-benzimidazolylmethyl)amine,    tetrakis(2-pyridylmethyl)ethylenediamine, 2,2′,2″-terpyridine,    1,4,7,10-tetraazadecane, 1,4,8,11-tetraazaundecane,    1,5,8,12-tetraazadodecane, 1,4,8,11-tetraazacyclotetradecane,    ethylenebis(biguanide), tetraphenylporphyrin,    tris(2-pyridylmethyl)amine, histidine and the like;-   (3) the carbonyl-containing compounds having 1 to 3 or more carbonyl    groups and 3 to 40 or more carbon atoms (excluding carboxylic acid);

ethyl acetoacetate, acetylacetone (hereinafter, referred to as acac),2,4-pentanedione, bis(acetylacetone), 3-methylpentane-2,4-dione,1-phenyl-1,3-butanedione, 3-phenylpentane-2,4-dione,1,3-diphenyl-1,3-propanedione, 1-phenyl-1,3,5-hexanetrione,5,5′-(1,2-ethanediyldinitrilo)bis(1-phenyl-1,3-hexanedione),trifluoroacetylacetone, hexafluoroacetylacetone, benzyl,dibenzoylmethane, aspartic acid benzoylacetone, thenoyltrifluoroacetone,4,4′-(1,2-ethanediyldinitrilo)bis(2-pentanone), dipivaloylmethane andthe like;

-   (4) carboxylic acids containing 1 to 4 or more carboxylic acid    groups and 2 to 20 or more carbon atoms;

oxalic acid, malonic acid, salicylic acid, phthalic acid, nicotinicacid, picolinic acid, aspartic acid, benzoylpyruvic acid,ethylenediaminediacetic acid, nitrilotriacetic acid,N′-(2-hydroxyethyl)ethylenediaminetriacetic acid,propylenediaminetetraacetic acid, ethylenediaminetetraacetic acid,trans-1,2-cyclohexanediaminetetraacetic acid,trans-1,2-(cyclohexanedinitrilo)tetraacetic acid,1,2-(ethanediyldinitrilo)tetraacetic acid, ethylenediaminetetrapropionicacid, glycine, N-methylglycine, glycylglycine,glycylglycylglycylglycine, salicylideneglycine, iminodiacid,methyliminodiacid, N,N-diethyldiselenocarbamic acid, methionine,proline, sarcosine, xanthic acid and the like;

-   (5) oximes having 1 to 4 or more oxime groups and 2 to 20 or more    carbon atoms;

dimethylglyoxime, 3-(2-aminoethylimino)-2-butanoneoxime,benzylmethylglyoxime, 2,6-diacetylpyridinedioxime, 2-pyridylaldoxime,3-phenylimino-2-butanoneoxime, salicylaldehydeoxime and the like;

-   (6) phenols having 1 to 4 or more phenol groups and 6 to 30 or more    carbon atoms;

catecol, 1,2-benzenediol, 1,3-bis[bis(2-pyridylethyl)aminomethyl]phenol,2,6-bis[bis(2-pyridylethyl)aminomethyl]-4-phenol, 1-nitroso-2-naphtholand the like;

-   (7) ethers having 1 to 8 or more ether groups and 4 to 30 or more    carbon atoms;

tetrahydrofuran, 1,4-dioxane, 1,4,7,10-tetraoxacyclotetradecane,1,4,7,10,13-pentaoxacyclopentadecane,1,4,7,10,13,16-hexaoxycyclooctadecane,4,7,13,16-tetraoxa-1,10-diazacyclooctadecane,4,7,13,18-tetraoxa-1,10-diazabicyclo[8,5,5]icosane,2,3-benzo-1,4,7,10,13-pentaoxacyclopentade-2-cen,4,7,13,16,21-pentaoxa-1,10-diazabicyclo[8,5,5]tricosane, monensin,nigericin and the like;

-   (8) sulfur compounds having 1 to 4 or more sulfur atoms and 2 to 40    or more carbon atoms;

diethyldithiocarbamic acid, ethylthioglycolic acid,ethylenebisthioglycolic acid, ethylenethiourea, phenyldithioacetic acid,dithiobenzoic acid, 1,2-aminoethanethiol, diphenylthiocarbazone,dimethylsulfoxide, 2,4-pentanedithione,2,2,7,7-tetramethyl-3,6-dithiaoctane, 2-imidazolidinethione,dimethyldithiocarbamic acid, thiourea, cysteine, maleonitriledithiol,1,4,8,11-tetrathiaundecane and the like;

-   (9) amide compounds having 1 to 3 or more amide groups and 3 to 54    or more carbon atoms;

diazoamide, N,N-dimethylacetamide, N,N-dimethylformamide,hexamethylphosphoric triamide, diphenylphosphinic amide,aminoethylamide, oxamide, valinomycin, phthalimide, succinimide,valinomycin and the like;

-   (10) N-oxides having 1 to 3 or more N-oxide groups and 6 to 20 or    more carbon atoms;

α-picoline-N-oxide, γ-picoline-N-oxide, pyridine-N-oxide and the like;

-   (11) others;

nitrogen molecule, water, carbon monoxide, urea, salicylaldehyde,N-nitrosophenylhydroxylamine oxyhydrogen and the like.

-   3) As the conjugated system compound having 2 to 10 or more    unsaturated groups and 4 to 14 or more carbon atoms, those described    below can be mentioned;

1,5-cyclooctadiene (hereinafter, referred to as cod),1,3,5,7-cyclooctatetraene, cyclopentadienyl,pentamethylcyclopentadienyl, tropolone, 1,10-phenanthroline and thelike.

From the viewpoint of polymerizability for the vinyl group, a halogen(fluorine, chlorine, bromine and iodine) ion and a phosphorousatom-containing compound are preferable, and the anion of an atomselected from chlorine, bromine and iodine and a tertiary phosphinecompound are particularly preferred. Further, as a combination,preferably, the combination between the metal element (d1) selected fromthe VIII Group element of the 5^(th) period and the ligand (d2) of ananion or neutral molecule being a halogen ion and/or tertiary phosphinecompound can be mentioned.

With regard to the synthesis method of the complex compound (d), it isusually obtained by mixing a salt of (d1) (for example, a halide of ametal, and the like) and (d2) at room temperature. Further, there isalso a case in which a compound of interest is prepared after forming adifferent intermediate complex compound. The salt of (d1) and the ligandof (d2) may be mixed as they are or after each of them being dissolvedin a separate aqueous/solvent solution, or may be mixed in anaqueous/solvent solution. If necessary, they may be heated to from 30through 200° C. When a substance, which should be removed, is generated,it may be removed under reduced pressure. The compound (d) generated maybe taken out as it is or as a crystal, and then purified. As the solventused herein, for example, an alcohol-based solvent (methanol, ethanoland the like), ketone-based solvent (acetone, methyl ethyl ketone andthe like), amide-based solvent (N,N-dimethylformamide,N-methylpyrrolidone and the like), sulfoxide-based solvent (dimethylsulfoxide and the like), and a mixture of 2 or more of them may bementioned.

There are so many compounds for (d), and they can be synthesizedindividually by methods described in, for example, Angew. Chem. Int. Ed.Engl., Vol. 12, pp. 57 (1973); J. Chem. Educ., Vol. 50, pp. 343 (1973);Accts. Chem. Research, Vol. 3, pp. 105 (1970); Chem. Rev., Vol. 73, pp.487 (1973); Interscience-Wilry (1968); Chem. Soc. Rev., Vol. 4, pp. 27(1975); Basic Inorganic Chemistry (written by F. A. Cotton and G.Wilkinson, Baifukan Co., Ltd.); Inorganic Compound-Complex Dictionary(K. Nakahara, Kodansha Ltd.), etc.

The mode of coordination is not specifically limited, and there aremonodentate (for example, triphenylphosphine as a ligand), bidentate(for example, ethylenediamine as a ligand), multidentate mode having 3to 6 coordination sites (for example, terpiridine as a ligand), but acombination of these coordination modes is usually applied. Further, (d)is usually a non electrolyte type complex compound having no charge, butmay be an electrolyte type complex compound having charge such as acomplex cation and a complex anion.

As (d), those described below may be specifically mentioned.

As specific examples,

-   (1) when (d1) is the IB Group element metal, [Cu(CH₃)(PPh₃)],    [Cu₂Cl(cod)₂], [Ag(py)₂]Cl, [Ag(py)₄]Cl, [Ag(py)₄]Cl₂, [AuCl(PPh₃)],    [AuCl₃(PPh₃)], and [Au(dppe)]Cl, or the like;-   (2) when (d1) is the VIII Group element metal of the 4^(th) period,    [FeCl₂(bpy)₂], [FeCl₂(bpy)₂]Cl, [FeCl(H)(CO)(PPh₃)₃],    [FeCl(H)(dppe)₂], [FeCl₃(NO)(PPh₃)₂], [FeCl₂(PPh₃)₃],    [FeCl₂(PPh₃)₄], [Fe(CN)₂(bpy)₂], [Fe(CO)₂(PPh₃)₃],    [Fe(H)₂(N₂)(PPh₃)₃], [CO₂Cl₂(cod)₂], [CoCl(CO)(PPh₃)₂],    [CoCl(PPh₃)₃], [CoCl(O₂)(PPh₃)₃], [CoCl₃(py)₃], [Co(cod)₂]Cl,    [Co(H)(CO)(PPh₃)₃], [Ni(acac)Cl(PPh₃)], [NiBr(CH₃){P(C₂H₅)₃}₂],    [NiBr(NH₃)₃], [Ni(CH₃)Cl(cod)], [Ni(C₂H₅)(cod)]Cl, [Ni(CH₃)(PPh₃)],    [Ni₂Cl₂(acac)₂], [NiCl₂(bpy)], [NiCl₂(cod)], [Ni₂Cl₂(dppm)],    [NiCl₂(en)], [NiCl₂(NH₃)(PPh₃)], [NiCl₂(PPh₃)], [Ni₂Cl₄(PPh₃)₂],    [Ni(PPh₃)₄], [Ni(py)₄]Cl₂, [Ni(SO₃)(H₂O)₃], and [Ni(SO₃)(NH₃)₃, or    the like;-   (3) when (d1) is the VIII Group element metal of the 5^(th) period,    [Rh₂Cl₂(cod)₂], [RhCl(CO)(PPh₃)₂], [RhCl(PPh₃)₃], [RhCl(O₂)(PPh₃)₃],    [RhCl₃(py)₃], [Rh(cod)₂]Cl, [Rh(H)(CO)(PPh₃)₃], [RuCl₂(bpy)₂],    [RuCl₂(bpy)₂]Cl, [RuCl(H)(CO)(PPh₃)₃], [RuCl(H)(dppe)₂],    [RuCl₃(NO)(PPh₃)₂], [RuCl₂(PPh₃)₃], [RuCl₂(PPh₃)₄], [Ru(CN)₂(bpy)₂],    [Ru(CO)₂(PPh₃)₃], [Ru(H)₂(N₂)(PPh₃)₃], [Pd(acac)Cl(PPh₃)],    [PdBr(CH₃){P(C₂H₅)₃}₂], [PdBr(NH₃)₃], [Pd(CH₃)Cl(cod)],    [Pd(C₂H₅)(cod)]Cl, [Pd(CH₃)(PPh₃)], [Pd₂Cl₂(acac)₂], [PdCl₂(bpy)],    [PdCl₂(cod)], [Pd₂Cl₂(dppm)], [PdCl₂(en)], [PdCl₂(NH₃)(PPh₃)],    [PdCl₂(PPh₃)], [Pd₂Cl₄(PPh₃)₂], [Pd(PPh₃)₄], [Pd(py)₄]Cl₂,    [Pd(SO₃)(H₂O)₃], and [Pd(SO₃)(NH₃)₃], or the like;-   (4) when (d1) is the VIII Group element metal of the 6^(th) period,    [OsCl₂(bpy)₂], [OsCl₂(bpy)₂]Cl, [OsCl(H)(CO)(PPh₃)₃],    [OsCl(H)(dppe)₂], [OsCl₃(NO)(PPh₃)₂], [OsCl₂(PPh₃)₃],    [OsCl₂(PPh₃)₄], [Os(CN)₂(bpy)₂], [Os(CO)₂(PPh₃)₃],    [Os(H)₂(N₂)(PPh₃)₃], [Ir₂Cl₂(cod)₂], [IrCl(CO)(PPh₃)₂],    [IrCl(PPh₃)₃], [IrCl(O₂)(PPh₃)₃], [IrCl₃(py)₃], [Ir(cod)₂]Cl,    [Ir(H)(CO)(PPh₃)₃], [Pt(acac)Cl(PPh₃)], [PtBr(CH₃){P(C₂H₅)₃}₂],    [PtBr(NH₃)₃], [Pt(CH₃)Cl(cod)], [Pt(C₂H₅)(cod)]Cl, [Pt(CH₃)(PPh₃)],    [Pt₂Cl₂(acac)₂], [PtCl₂(bpy)], [PtCl₂(cod)], [Pt₂Cl₂(dppm)],    [PtCl₂(en)], [PtCl₂(NH₃)(PPh₃)], [PtCl₂(PPh₃)], [Pt₂Cl₄(PPh₃)₂],    [Pt(PPh₃)₄], [Pt(py)₄]Cl₂, [Pt(SO₃)(H₂O)₃], and [Pt(SO₃)(NH₃)₃], or    the like can be mentioned, though, they are not for the limiting    purpose and therefor the compounds within the scope previously    described may be employed.

A preferred complex compound is such as [RuCl₂(PPh₃)₃], [RuCl₂(PPh₃)₄],[Pd₂Cl₂(dppm)], [RhCl(CO)(PPh₃)₂] and [RhCl(PPh₃)₃], i.e., the onecontaining the VIII Group element metal (ruthenium, rhodium, palladium)of the 5^(th) period and a ligand selected from a group consisting of ananion of an atom, which atom is selected from chlorine, bromine andiodine, and a tertiary phosphine compound.

Further, from the viewpoints of polymerizability and operability, it ispreferable that (d) is a complex compound which is soluble in water or awater-soluble organic solvent. As the water-soluble organic solvent, thesame solvent as used for the synthesis of the (d) may be mentioned.

The amount of (d) and (d1) is preferably 0.005 ppm to 2.0% by mass for(d) and 0.001 ppm to 1.0% by mass for (d1) based on the total mass of amonomer and first crosslinking agent, and more preferably 0.0.1 ppm to1.0% by mass for (d) and 0.005 ppm to 0.5% by mass for (d1), and mostpreferably, 0.02 ppm to 0.6% by mass for (d) and 0.01 ppm to 0.3% bymass for (d1).

When the amount of (d) is 0.005 ppm to 2% by mass and the amount of (d1)is 0.001 ppm to 1% by mass, the ability as an absorbable article isperformed, and productivity is good as well because the polymerizationspeed and the polymerization yield are to be sufficient.

When the solubility of (d) to an aqueous polymerization liquid is low,the polymerization can also be carried out by using a water-solubleorganic solvent and surfactant in combination and by dissolving ordispersing them in the aqueous polymerization liquid of the monomer.

The water-absorbable resin (A) obtained by the method can be furthercrosslinked if necessary by kneading the resin in a state of awater-containing gel with the crosslinking agent (a-2) or polyvalentmetal compound capable of forming an ionic crosslinkage (such as calciumchloride, magnesium sulfate, aluminum sulfate) or the like. Relativelyhomogeneous crosslinking is thereby obtained, thus the water-absorbableresin having high gel strength and fewer amounts of water-solublecomponents can be produced.

The effect of the present invention can be further improved when theabsorbable resin (A) is crosslinked with a crosslinker (the secondcrosslinking agent) at its surface, wherein the surface-crosslinkedresin is formed by crosslinking the vicinity of the surface of acrosslinked polymer obtained by drying and by subsequently pulverizingthe water-containing gel-stated polymer of the absorbable resin producedfrom the above method, and, if necessary, by adjusting the grain size ofthe pulverized polymer.

The drying method may be usual methods such as a drying method by hotair at a temperature of 80 to 230° C., thin film drying method using adrum dryer heated at 100 to 230° C., (heated) reduced pressure dryingmethod, freeze drying method and drying method by infrared rays. Also,there is no limitation for the pulverizing method, and common equipmentsuch as a hammer type pulverizer, impact type pulverizer, roll typepulverizer and jet stream type pulverizer may be used. The obtainedpulverized material, if necessary, are sieved to adjust its grain size.The form of the crosslinked polymer after pulverization is notspecifically limited, and irregular pulverized form, flake form, pearlform, rice grain form, granulated form and the like can be exemplified.For the usage in paper diapers and the like, the irregular pulverizedform is preferable from the viewpoints that it entangles well with afibrous material and that its falling from the fibrous material may notbe anticipated.

The grain size of the obtained water-absorbable resin (A) in theparticle form is controlled by sieving when needed. The mass averageparticle diameter of (A) obtained is preferably 100 to 800 μm, andfurther preferably 200 to 500 μm and, the one which was pulverized tohave 95% by mass or more of particles within a range of 100 to 850 μmcan be used. It is preferable that the content of a fine particle isless. The content of the particle of 100 μm or less is preferably 3% orless, and more preferably, the content of the particle of 150 μm or lessis 3% or less. The mass average particle diameter is measured accordingto a method by plotting the respective grain size distribution of thewater-absorbable resin on a logarithmic probability paper in which ahorizontal axis represents the particle diameter and a longitudinal axisrepresents the content based on mass, and determining a particlediameter which contains the 50% point of the total mass.

As the method of surface-crosslinking the water-absorbable resin (A),the conventional method, for example, a method of mixing a mixedsolution containing the second crosslinking agent (a-3), water and anorganic solvent with (A) and reacting the mixture with heat can bementioned.

The agent (a-3) may be the same or different as (a-2) above, however,the crosslinking agent (iii) having at least two functional groups whichcan react with an acid group such as a carboxylic acid and/or a group oftheir salts is preferable, and a polyglycidyl ether compounds such asethylene glycol diglycidyl ether, polyamine resin and azilidine compoundare preferable in particular from the viewpoint that they can conductthe surface-crosslinking at a comparatively low temperature.

The amount of (a-3) used is preferably 0.001 to 7.0% by mass based onthe total amount of (a-1), (a-2) and (a-3), more preferably 0.002 to5.0% by mass, and particularly preferably 0.003 to 4.0% by mass. Whenthe amount of (a-3) used is 0.001% by mass or more, the degree ofsurface-crosslinking is adequate, and the effect of improvement for theabsorption amount under a load is also to be sufficient. On the otherhand, when the amount of (a-3) used is 7.0% by mass or less, the degreeof surface-crosslinking is not excessive, and the amount of thewater/blood retention is not lowered.

The amount of water used when the surface-crosslinking is conducted ispreferably 1 to 10% based on the mass of the water-absorbable resin (A)and more preferably 2 to 7%. When the amount of water used is 1% ormore, the permeation of (a-3) to the inside of particles of thewater-absorbable resin (A) is to be sufficient, and the improvementeffect of the absorption amount under a load, particularly, theabsorption amount under a heavy load (for example, 60 g/cm²) is to begood. On the other hand, when the amount of water used is 10% or less,the permeation of (a-3) to the inside of (A) is not excessive, theimprovement of the absorption amount under a load is confirmed, and theproblem of a great decrease in the water/blood retention amount does notoccur.

In the present invention, as the kind of the organic solvent used incombination with water, a conventionally known hydrophilic solvent canbe used, and it can be suitably selected with the consideration of thedegree of permeation of (a-3) to the inside of (A) and of the reactivityof (a-3) and the like. The hydrophilic organic solvents capable of beingdissolved in water, such as methanol and diethylene glycol, arepreferable. These solvents may be used alone, or 2 or more of them maybe used in combination.

The amount of the solvent used can be variously changed depending on thekind of the solvent, but is preferably 1 to 10% based on the mass of(A). Further, the ratio of the solvent to water can be also arbitrarilychanged, and is preferably 20 to 80% based on mass and more preferably30 to 70%.

A mixed solution containing (a-3), water and a solvent is added to andmixed with (a2) by a conventionally known method, and a reaction withheat is carried out. The reaction temperature is preferably 80 to 200°C. and more preferably 100 to 160° C. The reaction time can be changeddepending on the reaction temperature, but is preferably 3 to 60 minutesand more preferably 5 to 40 minutes.

The particulate water-absorbable resin (A) obtained bysurface-crosslinking like this can be further additionallysurface-crosslinked by the same kind of (a-3) or the different kind of(a-3).

The thus obtained particulate water-absorbable resin (A) is sieved andthe grain size is adjusted if necessary. The mass average particlediameter of (A) obtained is hardly changed compared to that beforesurface-crosslinking, and preferably 100 to 800 μm and furtherpreferably 200 to 500 μm. The resin which was pulverized to have 95% bymass or more particles within a range of 100 to 850 μm can be used. Itis preferable that the content of fine particles is less. The content ofparticles of 100 μm or less is preferably 3% or less, and morepreferably the content of particles of 150 μm or less is 3% or less.

These surface-crosslinked type crosslinked copolymer is preferablebecause its absorption performance is superior not only under normalpressure but also under a load, and because its gel strength increases.

The average particle diameter of the water-insoluble nonporous sphericalmonoparticles (B) having an average particle diameter of 1 to 50 nm usedin the present invention is preferably 3 to 40 nm, more preferably 5 to35 nm and most preferably 10 to 30 nm.

When the average particle diameter is less than 1 nm, the diffusion andabsorption speed of a liquid to the inside of the resin in the obtainedabsorbent is bad. Further, when it exceeds 50 nm, the diffusion andabsorption speed of a liquid to the inside of the resin in the obtainedabsorbent is also bad. The average particle diameter can be measured byusual methods such as, for example, calculation from a value obtainedfrom the BET method, the Sears method or a laser method.

The particle (B) is a nonporous spherical monoparticle. With a porousparticle, the diffusion and absorption speed becomes bad. Further, itsform is spherical. Form other than spherical form such as, for example,hollow form, porous form, petal form, aggregated form or granulated formgenerates a problem in terms of handling. That said (B) has sphericalform can be grasped by observing the particles in a dispersed state bymeans of, for example, the transmission electron microscope (forexample, H-7100FA type, manufactured by Hitachi, Ltd.) under thecondition of accelerating voltage of 100 KV. Further, there is apreferable specific surface area for (B) from the viewpoint of theimprovement of the diffusion and absorption speed, and that is 50 to 400m²/g. It is more preferably 75 to 350 m²/g and particularly preferably100 to 300 m²/g. The specific surface area can be measured by the BETmethod, a Blaine method and the like. With regard to the spherical form,the roundness can be grasped, for example, by comparing the specificsurface area measured by the BET method with a value of the specificsurface area calculated from an average particle diameter measured by amethod other than the BET method with the assumption that the particleis monoparticle. The specific surface area (i) calculated from theaverage particle diameter of the particles of the invention in thepresent application is close to the measured value of the specificsurface area (ii) according to the BET method. It is preferable that thevalue of (i) is 90 to 110% relative to the value of (ii).

Aggregation of monoparticles is equal to being in the porous state sincespace is created among the aggregated particles, therefore, the averageparticle diameter will increase and the specific surface area willdecrease. Accordingly, the presence proportion between the monoparticles(primary particles) and the aggregated particles (secondary particles)can be controlled with the average particle diameter and specificsurface area. Although the primary particles of Aerosil 200 (silicamanufactured by Nippon Aerosil Co., Ltd.) is 60 nm or less, they areaggregated and not dispersed to be primary particles even if they aredispersed or solubulized in water, therefore the average particlediameter is usually 100 nm or more, so it is not used in the presentapplication. It is considered that this may be presumably because theprimary particles having been aggregated in the drying step in theproduction of the particles are hardly returned to their originalprimary particles even if they are dispersed in water. It is importantnot to dry the primary particles before use.

The kind of the material of (B) is not specifically limited as long asits average particle diameter is 1 to 50 nm and as long as it iswater-insoluble and nonporous, and the material may be either organic orinorganic.

As the example of organic nonporous spherical monoparticles, forexample,

-   (i) organic nonporous spherical monoparticles consisting only of the    carbon atom; polyethylene, polypropylene, polystyrene,    poly-β-xylylene, polybutadiene and the like,-   (ii) organic nonporous spherical monoparticles consisting of the    carbon atom and oxygen atom; a polyacrylate, polymethacrylate,    polyvinyl acetate, polyvinyl ether, thermoplastic polyester,    polycarbonate, polyphenylene oxide, polyepoxy, polyacetal, cellulose    derivative and the like,-   (iii) organic nonporous spherical monoparticles containing the    nitrogen atom; a polyacrylonitrile, polyamide, thermoplastic    polyurethane and the like,-   (iv) other organic nonporous spherical monoparticles; polyvinyl    chloride, polyvinylidene chloride, a fluororesin, polysulfone and    the like, and a polymer obtained by copolymerizing 2 or more    monomers which constitute these resins can be mentioned. The    example (i) is preferable. Further, the particles are required to    have a melting temperature equal to or higher than a temperature for    drying to prevent the organic nonporous spherical particles from    melting when the water-containing gel is dried. With respect to the    balance with the drying temperature, the melting temperature of the    organic nonporous spherical monoparticles is usually 130° C. or more    and preferably 150° C. or more.

The inorganic nonporous spherical monoparticles may be natural inorganicmaterials or synthetic inorganic materials, and for example, a siliconoxide, aluminum oxide, iron oxide, titanium oxide, magnesium oxide andzirconium oxide can be mentioned. Further, these may be used incombination of 2 or more of them, or 2 or more of them may form acomposite.

Among these, inorganic nonporous spherical monoparticles are preferable,a silicon oxide is further preferable, and amorphous silicon oxide ispreferable in particular.

When (B) is used as a water dispersion liquid or water-solublizingliquid having the (B) concentration of 10% by mass, the pH is notspecifically limited, but is usually 2 to 11, and preferably, 2.5 to 10from the viewpoint that (B) can exist stably as the primary particlesand the secondary aggregate does not generate at the pH.

The amount of the nonporous spherical monoparticles (B) against thewater-absorbable resin (A) is preferably 0.01 to 5.0% by mass, furtherpreferably 0.02 to 3.0% by mass, and particularly preferably 0.04 to2.5% by mass. When the amount of (B) added is 0.01% by mass or more, theeffect of improvement in diffusion and absorption speed to the inside ofthe resin is observed. When it is 5.0% by mass or less, the improvementin diffusion and absorption speed is attained, and at the same time, themechanical strength of the obtained absorbent particles is strong.Further, the absorption magnification of the obtained absorbents, theamounts of water/blood retention, and the absorption amount when pressedare not lowered.

The particle (B) is mixed with (A). (B) may be compounded at any step inthe manufacture process of (A) from the polymerization step to beforeand after the drying.

-   (i) When (B) is compounded before drying, it may be added to a    polymerization liquid to form a mixture by polymerization, in which    mixture (B) is compounded in a polymer (A) in the water-containing    gel state, or may be added to the polymerized polymer in the    water-containing gel state to form a mixture. The mixing may be    carried out by usual mixing equipment described below, and there is    no problem with the mixing temperature as long as it is between the    polymerization temperature and room temperature. The mixing time is    preferably for 30 minutes to 5 hours.

In this case, since the nonporous spherical monoparticles are compoundedto the resin in the water-containing gel state, diffusion and absorptionspeed of a liquid to the inside of the resin is improved by evaporatingmoisture in the water-containing gel, and therefore by storing(building) the nonporous spherical monoparticles in the inside of aresin.

-   (ii) When (B) is compounded after drying, the nonporous spherical    monoparticles cover the particle surface of (A), or (A) and the    nonporous spherical monoparticles exist separately as a simple    mixture of both. In this case, there are effects which not only    prevent the phenomenon of association among (A) via water, but also    prevent the phenomenon of provoking a decrease in performance caused    by coating the surface of (A) with the liquid to be absorbed    containing a water-insoluble matters and a water-hardly soluble    matters. It is considered that this is the same as the principle    using a filtration aid in order to prevent plugging when filtering    with a filter.

Methods of (i) and (ii) may be used in combination. In these methods themethod of (ii) is preferable.

(B) is in a condition of monoparticles, namely the condition of notaggregated, and it is preferable that the water dispersion liquid of(B), emulsified substance of (B) or water-solublizing state substance of(B) is mixed with (A). The method of mixing (B) in the water-solublizingstate with (A) is particularly preferred. Because thewater-solubilization tends to disperse the secondary particles into theprimary particles. The solubilized state indicates a phenomenon that asubstance insoluble in a solvent is visually observed to have beendissolved, and can be judged macroscopically. A colloid state is alsoincluded in the solubilized state. The solubilized state can be measuredby a transmission factor, and the transmission factor is preferably 80%or more and more preferably 90% or more. The transmission factor can bemeasured by a spectrophotometer. The water dispersion liquid orwater-solublizing state substance can be mixed by usual mixingequipment, but it is important that particles are not left in a drycondition from the time of production to the time of use. Because theparticles once dried become aggregated particles, and are hardlyre-dispersed even in water. The concentration of solid contents ispreferably 1 to 50% by mass, and more preferably 5 to 35% by mass. Thedispersing medium is preferably water, but if necessary, a water-solublesolvent (alcohols such as methanol, ethanol and the like, ketones suchas acetone and the like, esters such as ethyl acetate and the like) by70% by mass or less based on water may be used in combination. As themixing method, a method of mixing the water-solublizing state substanceof (B) with the dry powdery particles of (A), or a method of adding thewater-solublizing state substance of (B) to polymerized (A) beforedrying followed by mixing and then drying with heat may be mentioned,but the former is preferable. When the mixing is carried out using thesecond crosslinking agent, a method of simultaneously mixing the drypowdery particles of (A), the water-solublizing state substance of (B)and the second crosslinking agent followed by drying with heat wherein(A) is obtained by aqueous solution polymerization between awater-soluble monomer and the first crosslinking agent, or a method ofmixing the water-solublizing state substance of (B) after the drypowdery particles of (A) and the second crosslinking agent are mixed anddried with heat can be mentioned, but the latter is preferable.

Further, the water content in a mixture of the water-containing gel of(A) and (B) mentioned in the above method (i) is not specificallylimited, but is preferably 2 to 10-fold based on the solid contents of(A). When it is 2-fold or more, the uniformity at kneading is great, andthe improvement effect of the diffusion and absorption speed of theabsorbents obtained is good. When 10-fold or less, it is economicalbecause the drying time is short.

As the mixing equipment for compounding and homogeneously mixing (B)with (A) in a water-containing gel, conventionally known equipment canbe used. As the example of the specific equipment, a double arm typekneader, internal mixer (Banbury mixer), self cleaning type mixer, gearcompounder, screw type extruder, screw type kneader and a mincingmachine and the like can be mentioned. The combination of a pluralnumber of the equipment can also be used.

The drying temperature of the water-containing gel state mixture towhich (B) has been added is usually 60 to 230° C., preferably 100 to200° C., and in particular, preferably 105 to 180° C. With a dryingtemperature of 60° C. or more, it is economical because the drying timeis short, and when the temperature is 230° C. or less, a side reactionor the decomposition of the resin and the like do not occur, and alsothe absorption performance and the diffusion and absorption speed arenot lowered.

The equipment which dries a mixture of (B) and (A) in a water-containinggel state may be common equipment, and for example, a drum dryer,concurrent band dryer (tunnel dryer), ventilated band dryer, spoutingstream (nozzle jet) dryer, box type hot air dryer, infrared dryer, andthe like can be mentioned. The heat source is not specifically limited.The combination of a plural number of these dryers can be also used.

As an additive or an extending agent, a residual monomer reducing agent(for example, sodium sulfite, hydrogen peroxide and the like),surfactant, antibiotic (for example, a quaternary ammonium saltcompound, chlorohexidine compound, metal salt-based antibiotic and thelike), antiseptic, aromatizer, deodorant, colorant, antioxidant, andfine filler other than (B), and the like can be added in the mixture of(A) and (B) of the present invention if necessary. The addition amountis preferably 0.1 to 50% by mass based on (A) plus (B). These additivescan be added during the drying or also after drying of thewater-containing gel state mixture.

As a surfactant, there can be mentioned is an anion activator, nonionicactivator, cation activator, amphoteric activator, and for example, asurfactant described in the specification of U.S. Pat. No. 4,331,447.One or 2 or more of these may be used in combination.

Examples of anionic surfactants include hydrocarbon series ethercarboxylic acid having the carbon number of 8 to 24 or salts thereof[oxyethlene (polymerization degree=1 to 100) lauryl ether acetatesodium, oxyethlene (polymerization degree=1 to 100) laurylsulfosuccinate disodium etc.], hydrocarbon series sulfate ester saltshaving the carbon number of 8 to 24 [sodium lauryl sulfate, oxyethlene(polymerization degree=1 to 100) lauryl sulfate sodium, oxyethlene(polymerization degree=1 to 100) lauryl sulfate triethanolamine,oxyethlene (polymerization degree=1 to 100) coconut oil fatty acidmonoethanolamide sulfate sodium], hydrocarbon series sulfonate saltshaving the carbon number of 8 to 24 [sodium dodecylbenzenesulfonateetc.], hydrocarbon series phosphate salts having the carbon number of 8to 24 [sodium laurylphosphate, oxyethlene (polymerization degree=1 to100) lauryl ether phosphate sodium etc.], fatty acid salts [sodiumlaurate, lauric acid triethanolamine etc.], acylated amino acid salts[coconut oil fatty acid methyl taurine sodium, coconut oil fatty acidsarcosine sodium, coconut oil fatty acid sarcosine triethanolamine,N-coconut oil fatty acid acyl-L-glutamic acid triethanolamine, N-coconutoil fatty acid acyl-L-glutamate sodium, lauroylmethyl-β-alanine sodiumetc.], and others [sulfosuccinic acid oxyethlene (polymerizationdegree=1 to 100) lauroylethanolamide disodium etc.].

Examples of the nonionic surfactants include fatty acid series alcohols(carbon number of 8 to 24) alkyleneoxide (carbon number of 2 to 8)adduct (polymerization degree=1 to 100) [lauryl alcohol ethylene oxideadduct (polymerization degree=20), oleyl alcohol ethylene oxide adduct(polymerization degree=10), sperm alcohol ethylene oxide adduct(polymerization degree=35) etc.], oxyalkylene (carbon number of 2 to 8,polymerization degree=1 to 100) higher fatty acid (carbon number of 8 to24) ester [monostearic acid polyethylene glycol (polymerizationdegree=20), distearic acid polyethylene glycol (polymerizationdegree=30) etc.], polyhydric (2-hydric to 10-hydric or more-hydric)alcohol fatty acid (carbon number of 8 to 24) ester [monostearic acidglycerin, monostearic acid ethylene glycol, sorbitan lauric acid(mono/di) ester, sorbitan palmitic acid (mono/di) ester, sorbitanstearic acid (mono/di) ester, sorbitan oleic acid (mono/di) ester,sorbitan coconut oil (mono/di) ester stc.], polyoxyalkylene (carbonnumber of 2 to 8, polymerization degree=1 to 100) polyhydric (2-hydricto 10-hydric or more-hydric) alcohol higher fatty acid (carbon number of8 to 24) ester [polyoxyethylene (polymerization degree=10) sorbitanlauric acid (mono/di) ester, polyoxyethylene (polymerization degree=20)sorbitan palmitic acid (mono/di) ester, polyoxyethylene (polymerizationdegree=15) sorbitan stearic acid (mono/di) ester, polyoxyethylene(polymerization degree=10) sorbitan oleic acid (mono/di) ester,polyoxyethylene (polymerization degree=25) lauric acid (mono/di) ester,polyoxyethylene (polymerization degree=50) stearic acid (mono/di) ester,polyoxyethylene (polymerization degree=18) oleic acid (mono/di) ester,sorbitan, polyoxyethylene (polymerization degree=50) dioleic acid methylglucoside etc.], fatty acid alkanolamide [1:1 type coconut oil fattyacid diethanolamide, 1:1 type luric acid diethanolamide etc.],polyoxyalkylene (carbon number of 2 to 8, polymerization degree=1 to100) alkyl (carbon number of 1 to 22)phenylether(polyoxyethylene(polymerization degree=20)nonilphenyletheretc.), polyoxyalkylene (carbon number of 2 to 8, polymerization degree=1to 100) alkyl (carbon number of 8 to 24) aminoether and alkyl (carbonnumber of 8 to 24) dialkyl (carbon number of 1 to 6) amineoxide[lauryldimethylamineoxide etc.], polydimethylsiloxane ethyleneoxideadduct, polyoxyethylene polyoxypropylene block polymer (weight averagemolecular weight=150 to 10,000) and the like.

Examples of the cationic surfactants include quaternary ammonium salttype [stearyltrimethylammonium chloride, behenyltrimethylammoniumchloride, distearyldimethylammonium chloride, ethyl sulfate lanolinfatty acid aminopropylethyldimethylammonium etc.], amine salt type[stearic diethylaminoethylamide lactate, dilaurylamine hydrochloride,oleylamine lactate etc.], and the like.

Examples of the amphoteric surfactants include betaine type amphotericsurfactants [coconut oil fatty acid amidopropyldimethylaminoacetic acidbetaine, lauryldimethylaminoacetic acid betaine,2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine,laurylhydroxysulfo betaine, lauroylamidoethylhydroxyethylcarboxymethylbetaine hydroxypropylphosphate sodium etc.], amino acid type amphotericsurfactants [β-laurylaminopropionate sodium etc.], and the like.

Examples of the antioxident include hindered phenol series antioxidentsuch astriethyleneglycol-bis-[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate],1,6-hexanediol-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate],octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenylpropionate,3,5-di-t-butyl-4-hydroxybenzylphosphonate-diethyl ester and the like;amine series antioxidants such as n-butylamine, triethylamine,diethylaminomethyl methacrylate and the like, a combination of 2 or moreof them.

Examples of the ultraviolet absorbing agent include benzotriazole seriesultraviolet absorbing agents such as2-(5-methyl-2-hydroxyphenyl)benzotriazole,2-(3,5-di-t-butyl-2-hydroxyphenyl)benzotriazole,2-(3,5-di-t-butyl-2-hydroxyphenyl)-5-chlorobenzotriazole,2-(3,5-di-t-amyl-2-hydroxypehnyl)benzotriazole and the like; triazineseries ultraviolet absorbing agents such as2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[(hexyl)oxy)-phenol and the like;benzophenone series ultraviolet absorbing agents such as2-hydroxy-4-n-octyloxybenzophenone and the like; oxalic acid anilideseries ultraviolet absorbing agents such as 2-ethoxy-2′-ethyloxalic acidbisanilide and the like, and a combination of 2 or more of them.

Examples of the inorganic powder include calcium carbonate, kaolin,talc, mica, bentonite, clay, sericite, asbestos, glass fiber, carbonfiber, glass powder, glass baloon, sand bar baloon, coal powder, metalpowder, ceramic powder, silica, zeolite, slate powder and the like. Theform thereof may be arbitrary and an average particle size is preferably0.1 micron to 1 mm.

Examples of the pigment include carbon black, titanium oxide, red ironoxide, minium, parared, Prussian blue and the like.

Examples of the organic fibrous material include natural fibers[cellulose sereis (cotton, sawdust, straw etc.) and others, grass coal,wool, microfibril, bacterial cellulose etc.], artificial fibers(cellulose series such as rayon, acetate etc.), synthetic fibers(polyamide, polyester, acryl etc.), pulp [mechanical pulp (ground pulpfrom log, Asplund method ground pulp etc.), chemical pulp (sulfite pulp,soda pulp, sulfate pulp, nitric acid pulp, chlorine pulp etc.),semichemical pulp, regenerated pulp (for example, materials prepared bymechanically crushing or grinding papers once made from pulps, orregenerated wastepaper pulp prepared by mechanically crushing orgrinding wastepapers etc.) and the like.

The absorbents of the present invention, when used for the sanitarygoods such as a paper diaper and napkin, is effective for improving adry feeling and for reducing the leakage, by setting the diffusion andabsorption speed to bovine blood (containing 3.8% of citric acid;hematocrit value=20% by volume) as 25 to 65 ml/g and preferably 28 to 60ml/g. Further, the absorbents of the present invention obtained bysurface-crosslinking has an improved initial absorption amount underload, and it is more effective when those absorbents are used for thesanitary goods such as a paper diaper and napkin since the dry feelingmay be improved and also the leakage may be lowered by setting thediffusion and absorption speed to bovine blood as 25 to 65 ml/g andpreferably 28 to 60 ml/g, and by setting the initial absorption amountunder load to bovine blood as 18 to 40 g/g and preferably 25 to 40 g/g.Further, with regard to physiological saline, the absorbents exceed inthe diffusion and absorption speed, the initial absorption amount underload and the water retention amount. Still, the hematocrit value ofbovine blood used can be adjusted using physiological saline or plasma.Moreover, although the value may be occasionally somewhat differentdepending on the bovine blood used, the superiority or inferiority ofthe absorbents can be judged. diffusion and absorption speed, theinitial absorption amount under load and the water retention amount.Still, the hematocrit value of bovine blood used can be adjusted usingphysiological saline or plasma. Moreover, although the value may beoccasionally somewhat different depending on the bovine blood used, thesuperiority or inferiority of the absorbents can be judged.

(Absorbable Constructs and Absorbable Articles)

The absorbents (C) of the present invention is extremely superior inabsorption properties such as the diffusion and absorption speed and theabsorption amount, and articles with excellent absorption performancecan be obtained by applying the absorbents to the various absorbableconstructs (F) and absorbable articles.

As the method of applying the absorbent (C) of the present invention tothe various absorbable constructs (F), the method below may be mentionedfor the manufacture of the absorbable constructs constituted from amatrix of (C) and a fibrous material (E), for example, a method

-   (1) by scattering (C) between layers of fibrous materials consisting    of pulp, heat-adherable fibers and so on arranged in layers;-   (2) by mixing (C) with fibrous materials consisting of pulp,    heat-adherable fibers and so on; or-   (3) by sandwiching (C) on demand together with fibrous materials by    2 or more sheets of water-absorbing paper or nonwoven fabric.

As (E), fibrous materials which have been conventionally used forabsorbable articles such as, for example, various flap pulp and cottonpulp can be mentioned, and raw materials (coniferous trees, broad-leavedtrees, etc.), production processes [chemical pulp, semi chemical pulp,chemi-thermo mechanical pulp polyethylene-based fibers,polypropylene-based fibers), polyester-based fibers (for example,polyethylene terephthalate-based fibers), polyolefin-polyester complexedfibers, polyamide-based fiber, polyacrylonitrile-based fibers and thelike may be mentioned.

The length and thickness of (E) are not specifically limited, andusually, the length is preferably in a range of 1 to 200 mm and thethickness is preferably in a range of 0.1 to 100 denier. Also the shapeis not specifically limited so far as it is fibrous, and web form,narrow cylindrical form, shredded split yarn, staple form, filament formand the like are exemplified.

The addition amount of the absorbent (C) of the present invention to theabsorbable constructs (F) can be variously changed in accordance withthe kind and size of the absorbable constructs and the aimed absorptionperformance, but the amount of (C) is preferably 30 to 95% by weightbased on the mass of (F) and more preferably, 40 to 95% by weight.

The absorbable articles of the present invention is preferably anabsorbable article provided with said absorbable constructs (F), aliquid-permeable sheet and an air-permeable back sheet, and morepreferably, an article as sanitary goods. As the sanitary goods, forexample, a paper diaper (paper diaper for children, paper diaper for anadult, and the like), napkin (sanitary napkin and the like), papertowel, pad (pad for incontinence, under pad for operation and the like),pet sheet (urine absorbing sheet for pets) and the like can bementioned. A napkin and a paper diaper are preferable.

EXAMPLES

The present invention is further illustrated below according to Examplesand Comparative Examples, however the present invention is not limitedtherewith. Further, the diffusion and absorption speed, the initialabsorption amount under load, the absorption amount under load and thewater retention amount of the obtained absorbents were measured bymethods described below. Hereinafter, % indicates % by mass unlessotherwise specifically defined.

[Measurement Method of Diffusion and Absorption Speed]

0.10 g of an absorbent adjusted to a grain size of 30 to 60 mesh by aJIS standard sieve is prepared as a sample.

The device shown in FIG. 1 is placed on a level stand. Further, it is tobe confirmed that the arrangement of the narrow duct 5 which is theinlet of air and that of the upper surface of the flat plate 6 arehorizontal.

The cock 1 at the lowest portion of a burette and the cock 2 at a sidehole are closed, and bovine blood (containing 3.8% of citric acid; thehematocrit value=20% by volume: manufactured by Towa Pure Chemicals Co.)is charged in the burette 4 from the top of the burette. Then, theuppermost portion of the burette is closed with the rubber stopper 3,and the graduation showing the volume of bovine blood in the burette isread before opening the cock 1 at the lowest portion and the cock 2 atthe side hole. The plain cloth nylon mesh 7 (5 cm×5 cm) of 63 μm openingis laid on the flat plate 6 which has a 3 mm pore, and 0.10 g of thesample 8 is placed on it. The absorption starts once the sample isplaced, therefore the measurement starts from this point of time, andthe amount absorbed after 2 minutes is measured by reading thegraduation of the burette. The 10-fold value of the decreased volume ofbovine blood in the burette by absorption of the blood is referred to asthe diffusion absorption amount.

[Measurement Method of the Initial Absorption Amount Under Load and theAbsorption Amount]

0.10 g of the sample of an absorbent adjusted to a grain size of 30 to60 mesh by a JIS standard sieve is charged and leveled in a cylindricalplastic tube (30 mmφ in inner diameter, 60 mm in height) at which a250-mesh nylon net was attached to the bottom. A weight having an outerdiameter of 30 mmφ is mounted on the absorbent, and thereby a load of 20g/cm² is applied. The plastic tube containing the absorbent is quietlyplaced at the center of a Petri dish (12 cmφ in diameter) containing 60ml of the bovine blood, with the nylon net side facing downward. Themass of the absorbent increased by absorbing the bovine blood ismeasured after 10 minutes and 60 minutes. The 10-fold value of theincreased weight after 5 minutes is referred to as the initialabsorption amount under load to the bovine blood, and the 10-fold valueof the increased weight after 60 minutes is referred to as theabsorption amount under load to the bovine blood.

[Measurement Method of Blood Retention Amount]

1.00 g of the sample of an absorbent adjusted to a grain size of 30 to60 mesh by a JIS standard sieve is charged in a tea bag (20 cm inlength, 10 cm in width) made by a 250-mesh nylon net. The tea bag isimmersed in 500 ml of the bovine blood for 60 minutes for absorption,then hung for 15 minutes to drain water, and further centrifuged fordewatering with a centrifugal force of 150G for 90 seconds by adewatering centrifuge. The increased mass is measured to obtain theblood retention amount with regard to the bovine blood.

Example 1

Into a 1 L glass reactor, 77 g of sodium acrylate, 22.8 g of acrylicacid, 0.2 g of N,N′-methylenebisacrylamide, 395 g of deionized water and0.001 g of dichlorotris(triphenylphosphine)ruthenium were charged andthe temperature of the content was kept at 3° C. while stirring andmixing.

After the dissolved oxygen amount was decreased to 1 ppm or less byinfluxing nitrogen into the content, 1 g of a 1% aqueous solution ofhydrogen peroxide, 1.2 g of a 0.2% aqueous solution of ascorbic acid and2.8 g of a 2% aqueous solution of 2,2′-azobisamidinopropanedihydrochloride were added and mixed to initiate polymerization. Thepolymerizing was continued for about 5 hours to obtain water-containinggel state water-absorbable resin (A1). After (A1) was ground to a sizeof 2 to 5 mm by an internal mixer, 0.1 g of ethylene glycol diglycidylether and 1 g of KLEBOSOL 30H25 (pH for 10% water dispersion liquid=2.5,average particle diameter=25 nm, specific surface area=120 m²/g, solidcontent 30%) (B1) manufactured by Clariant Japan Co., Ltd. which is theaqueous colloidal solution of nonporous spherical amorphous siliconoxide were added, the mixture was further homogeneously mixed by theinternal mixer, and then dried at a condition of 150° C. and an air flowrate of 2.0 m/sec. by a ventilated band drier (manufactured by InoueKinzoku Kogyo Co., Ltd.).

The dried product obtained was pulverized and adjusted to a grain sizeof 20 to 100 mesh to obtain the absorbent (1). The evaluation result ofperformance of the absorbent (1) is shown in Table 1.

Example 2

After the water-containing gel state absorbable resin (A1) obtained inExample 1 was ground to a size of 2 to 5 mm by an internal mixer, 0.1 gof ethylene glycol diglycidyl ether was added. The mixture was furtherhomogeneously mixed by the internal mixer, and then dried at a conditionof 150° C. and an air flow rate of 2.0 m/sec. by a ventilated band drier(manufactured by Inoue Kinzoku Kogyo Co., Ltd.). The dried productobtained was pulverized and adjusted to a grain size of 20 to 100 mesh.Next, 1 g of (B1) was added thereto and after the mixture was furtherhomogeneously mixed by the internal mixer, it was adjusted to a grainsize of 20 to 100 mesh to obtain the absorbent (2). The evaluationresult of performance of the absorbent (2) is shown in Table 1.

Example 3

After the water-containing gel state absorbable resin (A1) obtained inExample 1 was ground to a size of 2 to 5 mm by an internal mixer, thesame amount of (B1) as that in Example 1 was added to be mixed, and thenan absorbent having a grain size of 20 to 100 mesh was obtained in asimilar manner as in Example 1.2 g of a water/methanol mixed solution(water/methanol=30/70) containing 1% of ethylene glycol diglycidyl etherwas added to 10 g of the absorbent while stirring at high speed, andcrosslinked with heat at 140° C. for 30 minutes to obtain thesurface-crosslinked type absorbent (3). The evaluation result ofperformance of the absorbent (3) is shown in Table 1.

Examples 4 and 5

The surface-crosslinking type absorbents (4) and (5) were obtained inthe similar manner as in Example 1, except that the additional amount of(B1) in Example 2 was changed 1 g to 0.5 g or 3 g. The evaluationresults of performance of these are shown in Table 1.

Examples 6 and 7

The absorbents (6) and (7) were obtained in a similar manner as inExample 2, except that (B1) was replaced by the same amount of thebelow-mentioned nonporous spherical monoparticles (B2) or (B3) inExample 2. The evaluation results of performance of these absorbents areshown in Table 1.

-   (B2): KLEBOSOL 30CAL25 (pH for 10% water dispersion liquid=4.0,    average particle diameter=25 nm, specific surface area=200 m²/g,    solid content of 30%) manufactured by Clariant Japan Co., Ltd.-   (B3): KLEBOSOL 30R9 (pH for 10% water dispersion liquid=10.7,    average particle diameter=9 nm, specific surface area=300 m²/g,    solid content of 30%) manufactured by Clariant Japan Co., Ltd.

Examples 8 and 9

The absorbents (8) and (9) were obtained in a similar manner as inExample 2, except that dichlorotris(triphenylphosphine)ruthenium wasreplaced by the same amount of chlorotris(triphenylphosphine)rhodium ordichlorotetrakis(triphenylphosphine)ruthenium in Example 2. Theevaluation results of performance of these absorbents are shown in Table1.

Example 10

Into a 1 L glass reactor, 77 g of sodium acrylate, 22.75 g of acrylicacid, 0.25 g of N,N′-methylenebisacrylamide, 329.3 g of deionized waterand dichloro(tristriphenylphosphine)ruthenium were charged, 1 g of (B1)was added while stirring and mixing, and the temperature of the contentwas kept at 3° C.

After the dissolved oxygen amount was decreased to 1 ppm or less byinfluxing nitrogen into the content, 1 g of a 1% aqueous solution ofhydrogen peroxide, 1.2 g of a 0.2% aqueous solution of ascorbic acid and2.8 g of a 2% aqueous solution of 2,2′-azobisamidinopropanedihydrochloride were added and mixed to initiate polymerization. Thepolymerizing was continued for about 5 hours to obtain thewater-containing gel state absorbable resin (AB1) containing (B1).

After (AB1) was ground to a size of 2 to 5 mm by an internal mixer, itwas dried at a condition of 150° C. and an air flow rate of 2.0 m/sec.by a ventilated band drier. The dried product obtained was pulverizedand adjusted to have a grain size of 20 to 100 mesh to obtain anabsorbent. 2 g of a water/methanol mixed solution (water/methanol=30/70)containing 1% of ethylene glycol diglycidyl ether was added to 100 g ofthe absorbent while stirring at high speed, and crosslinked with heat at140° C. for 30 minutes to obtain the absorbent (10). The evaluationresult of performance of the absorbent (10) is shown in Table 1.

Example 11

Into a 1 L glass reactor, 81.75 g of acrylic acid, 0.25 g ofN,N′-methylenebisacrylamide and 341 g of deionized water were charged,and the temperature of the content was kept at 3° C. while stirring andmixing.

After the dissolved oxygen amount was decreased to 1 ppm or less byinfluxing nitrogen into the content, 1 g of a 1% aqueous solution ofhydrogen peroxide, 1.2 g of a 0.2% aqueous solution of ascorbic acid and2.8 g of a 2% aqueous solution of 2,2′-azobisamidinopropanedihydrochloride were added and mixed to initiate polymerization. Thepolymerizing was continued for about 5 hours to obtain acid typewater-containing gel state polymer.

The water-containing gel state polymer was ground to a size of 2 to 5 mmby an internal mixer while 109.1 g of a 30% sodium hydroxide aqueoussolution was added and kneaded to obtain 72% by mol of the carboxylicacid group neutralized water-containing gel state water-absorbable resin(A2).

After the same amount of (B1) as in Example 1 was added to thewater-containing gel state water-absorbable resin (A2) and homogeneouslymixed, the mixture was dried at a condition of 150° C. and an air flowrate of 2.0 m/sec. by a ventilated band drier.

The dried product obtained was pulverized and adjusted to a grain sizeof 20 to 100 mesh to obtain an absorbent. 2 g of a water/methanol mixedsolution (water/methanol=30/70) containing 1% of ethylene glycoldiglycidyl ether was added to 100 g of the absorbent while stirring athigh speed, and crosslinked with heat at 140° C. for 30 minutes toobtain the absorbent (11). The evaluation result of performance of theabsorbent (11) is shown in Table 1.

Comparative Example 1

After the water-containing gel state water-absorbable resin (A1)obtained in Example 1 was ground to a size of 2 to 5 mm by an internalmixer, 0.1 g of ethylene glycol diglycidyl ether was added, the mixturewas further homogeneously mixed by the internal mixer, and then dried ata condition of 150° C. and an air flow rate of 2.0 m/sec. by aventilated band drier.

The dried product obtained was pulverized and adjusted to a grain sizeof 20 to 100 mesh to obtain a comparative absorbent (a). The evaluationresult of performance of the comparative absorbent (a) is shown in Table1.

Comparative Example 2

After the water-containing gel state water-absorbable resin (A1)obtained in Example 1 was ground to a size of 2 to 5 mm by an internalmixer, it was dried at a condition of 150° C. and an air flow rate of2.0 m/sec. by a ventilated band drier. The dried product obtained waspulverized and adjusted to a grain size of 20 to 100 mesh to obtain anabsorbent. 2 g of a water/methanol mixed solution (water/methanol=30/70)containing 10% of ethylene glycol diglycidyl ether was added to 100 g ofthe absorbent while stirring at high speed, and crosslinked with heat at140° C. for 30 minutes to obtain the surface-crosslinked typecomparative absorbent (b). The evaluation result of performance of thecomparative absorbent (b) is shown in Table 1.

Comparative Example 3

After the water-containing gel state water-absorbable resin (A1)obtained in Example 1 was ground to a size of 2 to 5 mm by an internalmixer, 0.1 g of ethylene glycol diglycidyl ether and 10 g of a 3% waterdispersion liquid of AEROSIL200 (average particle diameter=220 nm,primary particle diameter=12 nm, specific surface area=200 m²/g)(comparative B1) manufactured by Nippon AEROSIL K.K. were added, themixture was further homogeneously mixed by the internal mixer, and thendried at a condition of 150° C. and an air flow rate of 2.0 m/sec. by aventilated band drier. The dried products obtained were pulverized andadjusted to a grain size of 20 to 100 mesh to obtain an absorbent. 2 gof a water/methanol mixed solution (water/methanol=30/70) containing 1%of ethylene glycol diglycidyl ether was added to 100 g of the absorbentwhile stirring at high speed, and crosslinked with heat at 140° C. for30 minutes to obtain the surface-crosslinked type absorbent (c). Theevaluation result of performance of the absorbent (c) is shown in Table1.

Comparative Example 4

After the water-containing gel state water-absorbable resin (A1)obtained in Example 1 was ground to a size of 2 to 5 mm by an internalmixer, 0.1 g of ethylene glycol diglycidyl ether was added, the mixturewas further homogeneously mixed by the internal mixer, and then dried ata condition of 150° C. and an air flow rate of 2.0 m/sec. by aventilated band drier (manufactured by Inoue Kinzoku Kogyo Co., Ltd.).Then, 0.3 g of (comparative B1) was added, the resulting mixture wasfurther homogeneously mixed by the internal mixer, and adjusted to agrain size of 20 to 100 to obtain the absorbent (d). The evaluationresult of performance of the absorbent (d) is shown in Table 1.

The results are shown in Table 1.

TABLE 1 Initial absorption Diffusion absorption amount Blood and amountunder retention Absor- absorption under load amount bent speed (ml/g)load (g/g) (g/g) (g/g) Example 1  (1) 29 24 32 44 Example 2  (2) 31 2634 46 Example 3  (3) 29 24 32 40 Example 4  (4) 30 25 33 45 Example 5 (5) 32 27 35 47 Example 6  (6) 32 26 34 47 Example 7  (7) 30 26 33 45Example 8  (8) 29 24 33 42 Example 9  (9) 29 24 32 41 Example 10 (10) 2923 32 40 Example 11 (11) 29 24 32 40 Comparative (a) 24 17 27 30 Example1 Comparative (b) 22 17 29 34 Example 2 Comparative (c) 25 20 30 36Example 3 Comparative (d) 23 17 28 36 Example 4

INDUSTRIAL APPLICABILITY

The absorbents of the present invention exhibit effect shown below evenin a liquid to be absorbed containing water-insoluble or hardlywater-soluble matters such as menstrual blood or feces.

-   1) Thanks to the fast diffusion and absorption speed and good    initial absorption amount under load (representing absorption speed    when load is applied), the advantages in the improvement of initial    dry feeling and the decrease in leaking are obtained when used as    absorbents, for example, sanitary goods.-   2) The water/blood retention amount and in the absorption amount    under load is also superior.-   3) Since they are the water-insoluble nonporous spherical    monoparticles having an average particle diameter of 1 to 50 nm,    they are excellent in handling property of powder. Moreover, like    the granulated fine particles, they hardly generate fine particles    caused by the destruction of the absorbent particle with the    mechanical shearing force or friction.-   4) Since the water-insoluble nonporous spherical monoparticles    having an average particle diameter of 1 to 50 nm, when they are    formed into absorbents by mixing with fibrous materials such as    pulp, they hardly fall from fibrous materials even if an external    force such as vibration is added.-   5) Unlike the improvement by a pyrolytic foaming agent, the    deterioration of performance does not occur during a production    process because radicals and such are not generated when they are    dried with heat. Therefore, absorbents not only having an excellent    diffusion and absorption speed and the absorption performance, but    also only having small amount of water-soluble components are    obtained.-   6) The improvement of the diffusion and absorption speed can be    designed by a simple method of mixing nonporous spherical    monoparticles during the step of polymerizing the water-absorbable    resin or at any step from after polymerization to after drying.

The use of the absorbable articles of the present invention ispreferably the above sanitary goods. Further, it is useful not only forsanitary goods, but also for various uses such as an urine gelling agentof a portable toilet, freshness preserver of greengrocery, dripabsorbent for such as meat, fish and shellfish, a cooling agent,disposable body warmer, gelling agent for cells, water retention agentfor such as plants and soil, dew inhibitor, sealant, packing materials,and artificial snow.

BRIEF DESCRIPTION OF DRAWING

FIG. 1 is a drawing showing a device for measuring the diffusion andabsorption speed of the present invention.

The description of codes is as described below.

-   1. Cock-   2. Cock-   3. Rubber stopper-   4. Burette-   5. Narrow duct-   6. Flat plate having a pore-   7. Nylon mesh-   8. Sample-   9. Bovine blood-   10. Atmospheric pressure

1. A process for producing an absorbent (C), comprising the steps of:(1) carrying out polymerization in the presence of a complex compound(d) of a metal element (d1) and ligand (d2) in which the ligand is ananion or a neutral molecule to obtain a water absorbable resin (A); and(2) mixing a water-insoluble nonporous spherical monoparticle (B) havingan average particle diameter of 1 to 50 nm in the water-solubilizedstate with said resin (A) in dry form, or admixing said (B) with saidresin (A) before drying and then drying the mixture under heating. 2.The process of claim 1, wherein said (B) is water-insoluble nonporousspherical monoparticle in the water-solublizing state.
 3. The process ofclaim 1, wherein the specific surface area of said (B) is 50 to 400m²/g.
 4. The process of claim 1, wherein said (B) is an inorganicwater-insoluble nonporous spherical monoparticle.
 5. The process ofclaim 4, wherein said (B) is amorphous silicon oxide.
 6. The process ofclaim 1, wherein said (A) is a water-absorbable resin obtained bypolymerizing a water-soluble monomer and a first crosslinking agent inan aqueous solution.
 7. The process of claim 1, wherein said metalelement (d1) is a metal element selected from the VIII Group of the4^(th) to 6^(th) period and IB Group in the Periodic Table of the longperiod.
 8. The process of claim 1, wherein said ligand (d2) of an anionor a neutral molecule is one or two or more of the ligand selected froma group consisting of the below-mentioned (1) through (3); (1) the anionof an atom selected from hydrogen and halogen (2) a compound having oneor two or more of atoms selected from nitrogen, oxygen, phosphorous andsulfur, (3) a conjugated compound.
 9. The process of claim 1, whereinsaid metal element (d1) is selected from the VIII Group of the 5^(th)period and said ligand (d2) of an anion or a neutral molecule is ahalogen ion and/or a tertiary phosphine compound.
 10. The process ofclaim 1, wherein the amount of said (B) to (A) is 0.01 to 5% by mass.11. The process of claim 1, wherein the average particle diameter ofsaid (B) is 10 to 30 nm.
 12. The process of claim 6, wherein said (A) isobtained by polymerizing a water-soluble monomer and a firstcrosslinking agent in an aqueous solution, and is furthersurface-crosslinked by a second crosslinking agent.
 13. The process ofclaim 12, wherein said (A) is a water-absorbable resin obtained bypolymerization in the presence of a complex compound (d) of a metalelement (d1) and the ligand (d2) of an anion or a neutral molecule, andsaid (B) is amorphous silicon oxide.
 14. A process of producing theabsorbent (C) according to claim 1, wherein the water-solublizing statesubstance of water-insoluble nonporous spherical monoparticle (B) havingan average particle diameter of 1 to 50 nm and the second crosslinkingagent are simultaneously mixed with the dry powdery particle of said (A)obtained by aqueous solution polymerization between the water-solublemonomer and the first crosslinking, and then the mixture is dried withheat, or wherein the dry powdery particles of said (A) and the secondcrosslinking agent are mixed and dried with heat, and then thewater-solublizing state substance of (B) is mixed.
 15. A process forproducing an absorbable construct (F), comprising the steps of: (1)carrying out polymerization in the presence of a complex compound (d) ofa metal element (d1) and ligand (d2) in which the ligand is an anion ora neutral molecule to obtain a water absorbable resin (A); (2) mixing awater-insoluble nonporous spherical monoparticle (B) having an averageparticle diameter of 1 to 50 nm in the water-solubilized state with saidresin (A) in dry form, or admixing said (B) with said resin (A) beforedrying and then drying the mixture under heating to produce an absorbent(C); and (3) manufacturing the absorbable construct (F) composed of amatrix of the absorbent (C) and a fibrous material (E), wherein theabsorbent (C) is present in an amount of 30 to 95% by weight based onthe absorbable construct (F).
 16. A process for producing an absorbablearticle (G), comprising the steps of: (1) carrying out polymerization inthe presence of a complex compound (d) of a metal element (d1) andligand (d2) in which the ligand is an anion or a neutral molecule toobtain a water absorbable resin (A); (2) mixing a water-insolublenonporous spherical monoparticle (B) having an average particle diameterof 1 to 50 nm in the water-solubilized state with said resin (A) in dryform, or admixing said (B) with said resin (A) before drying and thendrying the mixture under heating to produce an absorbent (C); (3)manufacturing the absorbable construct (F) composed of a matrix of theabsorbent (C) and a fibrous material (E), wherein the absorbent (C) ispresent in an amount of 30 to 95% by weight based on the absorbableconstruct (F); and (4) preparing the absorbable article (G) providedwith the absorbable construct (F), a liquid-permeable sheet and anair-permeable back sheet.
 17. The process of claim 16, the absorbablearticle (G) being sanitary goods comprising a paper diaper, napkin, pad,paper towel or pet sheet.